Useful notes on the Test for Amylase Activity
No change in colour of iodine solution will indicate the presence of amylase enzyme. Take another part of the extract, add few drops of Benedict’s solution and heat it till it boils.
A brick-red precipitate will confirm the presence of amylase enzyme in the extract. Repeat the above two tests with the control mixture.
In the first test violet colour will confirm the presence of starch as such which has not been digested.
Starch always gives bluish-violet colour with iodine solution. In the experimental solution the enzyme extract is mixed with iodine solution, the amylase present in the enzyme extract hydrolyses the starch into maltose and glucose, therefore, there is no change in the colour of iodine.
In the control experiment amylase is destroyed by boiling the enzyme extract, the starch is not hydrolyzed into maltose and glucose, therefore, it gives bluish-violet colour with the iodine solution.
In the second test with Benedict’s solution a red precipitate of cuprous oxide appears. In this glucose is formed. Since glucose is a reducing sugar, it reduces copper sulphate into cuprous oxide.